Treatment of Lactose with Alkaline Methanolic Solutions: Production of Beta-Lactose from Alpha-Lactose Hydrate

Abstract

Crystallization of lactose from methanolic solutions of sodium hydroxide can be used to prepare β-lactose from α-lactose hydrate. Conversion of 90 to 93% α-lactose hydrate to β-lactose can be achieved by 2 h refluxing with any ratio of lactose to methanol as long as the methanol contains from .02 to .06% (wt/vol) sodium hydroxide and less than 13% (wt/wt) moisture. At room temperature, conversion was complete in 10 h at all ratios of α-lactose hydrate to methanol containing from .1 to .3% (wt/vol) sodium hydroxide and no more than 3% (wt/wt) moisture. The conversion of α-lactose hydrate to β-lactose ceased when moisture was above 3.5% (wt/wt) at room temperature and 13% (wt/wt) at reflux. With sodium hydroxide concentrations above .06%, at reflux, or above .3% at room temperature, alkaline rearrangement took place, and lactose was converted into a yellow mixture of degradation products. © 1978, American Dairy Science Association. All rights reserved.